The board should be no more than 60 mm wide, and no more than 210 mm long. In fact, limiting the length to 190 mm would be preferable. Also, the tallest components on the board should ideally be located on one half of the board, so that it would properly fit underneath another PCB that will be mounted at an angle.

Dual-Board Design

If necessary, the DAC board could be split into two separate boards, one for the 8 individual stereo channels, and one of the mixed stereo channel. In this case, the 8-channel board would have 2 ES9018 devices, while the single-channel board would have just one.

Mix Channel

The mix channel circuit (with single or dual board design) should be optimized to provide the best possible DAC design, with little consideration for cost. Sound quality is of the essence.

1 GHz Rogers board, 2 oz copper, gold finish

6 GHz U.FL coax headers for digital inputs

Up to 1.5 MHz sampling rate

Stereo or dual mono operation

Synchronous or asynchronous operation

Optimized direct connections (no jumpers, switches, or links)

Separate power supply inputs with on-board filters and regulators

Low noise low-dropout regulator for digital power

Precision ultra-pure supply for analog power (<0.5uV rms noise)

Regulators for analog power

Inputs

Ideally, each stereo channel should be exposed through its own I²S input (9 stereo channel in total). This is due to the fact that we will want to route a pair of stereo inputs to each of the four Parallella submodules that will be mounted on our backplane, and another pair to one of the submodule, the latter one being responsible for mixing our 8 stereo channels in the digital domain.

Ouputs

The outputs should use headers instead of RCA or DB25 connectors, because we’re likely to add a dedicated printed circuit board for the backplate. This would allow us to decouple the development of our ADC and DAC boards from the development of our backplate and from the layout of our backplate connectors. This is especially important because the number of USB and RJ45 connectors exposed on the backplate is subject to change, depending on our ability to support the AVB and USB 3.0 protocols.

Power Supply Regulators

Ideally, all components for power supply regulation should be directly mounted on the DAC board, instead of being mounted on breakout boards. This design will help reduce the height of the DAC board, which needs to be mounted underneath another PCB within a fairly small enclosure.

Self-Contained Design

Ideally, the DAC board should be fully self-contained, meaning that it could be connected to the PSU board and to the backplane with simple cables, and no other electronic components. Connectivity to the backplane will be achieved through a set of GPIO pins offered by the Xilinx Zynq-7020. Any component required for connecting the DAC board to the backplane should be directly added to the DAC board itself. This includes components that might be required for controlling the ES9102C converters and could not be provided by simply programming the Xilinx FPGA.